Differential-Mode EMI Calculator

Signal trace segments and their correspoding return paths represent a potential source of radiated emissions. The maximum radiated electric field due to differential currents flowing on traces can be estimated using a closed-form expression [1]. The algorithm used to make the calculations below is described in [2].

Assumptions:
  • All dimensions are small compared to the wavelength of interest.
  • The net current flowing in one direction (i.e. the common-mode current) is zero.

Printed Circuit Board Trace


Trace Height=  mm
Trace Length=  mm

circuit board trace over plane

Voltage Source

Amplitude (A): V
Rise time (tr): ns
Fall time (tf): ns
Duty cycle (τ/T): %
Data rate: Mbps
Trace load
Resistance (RL):  Ohm
Capacitance (CL):  pF

Important Note: This algorithm was revised in January 2014. The new algorithm does not ask for the source impedance. The voltage input by the user is the signal voltage, not the open-circuit source voltage. The signal current is the signal voltage divided by the load impedance.

[1] C. Paul, Introduction to Electromagnetic Compatibility, New York: Wiley, 1992.

[2] C. Zhu and T. Hubing, "Maximum Radiated Emission Calculator: Differential-Mode EMI Algorithm," CVEL-13-052, Oct. 13, 2013.

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